The present invention relates to a refrigerator having a liquid heat exchanger and an air heat exchanger.
Conventionally, there has been a refrigerator for simultaneously feeding cold water and hot water, which is composed of a compressor for compressing a refrigerant, a hot water heat exchanger, an expander, a cold water heat exchanger and an air heat exchanger, with a three-way valve mounted on an outlet side of the compressor and a three-way valve mounted on an inlet side of the compressor (see JP S56-7955 A).
In the conventional refrigerator, when the cold water heat exchanger is larger in heat load than the hot water heat exchanger, the opening degree of the outlet-side three-way valve is regulated so as to communicate the outlet side of the compressor with the hot water heat exchanger and the air heat exchanger, while the opening degree of the inlet-side three-way valve is regulated so as to communicate the inlet side of the compressor with the cold water heat exchanger. Consequently, the air heat exchanger functions as a condenser, by which the heat load is balanced between the cold water heat exchanger having a relatively large heat load and the hot water heat exchanger having a relatively small heat load.
When the hot water heat exchanger is larger in heat load than the cold water heat exchanger, the opening degree of the outlet-side three-way valve is regulated so as to communicate the outlet side of the compressor only with the hot water heat exchanger, while the opening degree of the inlet-side three-way valve is regulated so as to communicate the inlet side of the compressor both with the cold water heat exchanger and the air heat exchanger. Consequently, the air heat exchanger functions as an evaporator, by which the heat load is balanced between the hot water heat exchanger having a relatively large heat load and the cold water heat exchanger having a relatively small heat load.
However, in the conventional refrigerator, when the air heat exchanger functions as a condenser, air used in air heat exchange is usually lower in temperature than hot water for heat exchange in the hot water heat exchanger, which makes condensing pressure of the refrigerant in the air heat exchanger lower than the condensing pressure of the refrigerant in the hot water heat exchanger. Therefore, since a flow rate of the refrigerant in the air heat exchanger becomes smaller than that of the refrigerant in the hot water heat exchanger, the refrigerant grows stagnant, i.e., the flooding phenomenon as it is called occurs. As a result, the conventional refrigerator suffers a problem that an amount of the refrigerant required to be retained in a refrigerant circuit is larger than that in a normal refrigerator having only a cold water heat exchanger and an air heat exchanger. For example, in the case where the hot water heat exchanger performs heat exchange using hot water with a temperature of about 45° C. at an outdoor temperature of −5° C., there is such a problem that the conventional refrigerator needs a refrigerant twice as much as the refrigerant used in the normal refrigerator.
Moreover, when the heat loads in the hot water heat exchanger and the cold water heat exchanger changes and the heat load of the hot water heat exchanger becomes larger than the heat load of the cold water heat exchanger, the outlet-side and inlet-side three-way valves are regulated so that the air heat exchanger which has been functioning as the condenser functions as an evaporator. In this case, a large amount of a liquid refrigerant stagnant in the air heat exchanger due to the flooding phenomenon may flow into the compressor, and may cause liquid back to the compressor, which may lead to breakdown.